RING-OPENING OLIGOMERIZATION OF 3,3-DIMETHYLTHIETANE BY A TRIOSMIUM CLUSTER COMPLEX

The complexes Os3(CO)11(SCH2CMe2CH2) (1) and Os3(CO)10(mu-SCH2CMe2CH2) (2) were synthesized by the reactions of 3,3-dimethylthietane (3,3-DMT) with Os3(CO)11(NCMe) and Os3(CO)10(NCMe)2, respectively. Complex 2 was characterized crystallographically and was found to contain an S-coordinated bridging DMT ligand. Compound 2 reacts with 3,3-DMT at 25-degrees-C to yield the complex Os3(CO)10[mu-SCH2CMe2CH2)3] (3), which contains an 11-osmio-2,2,6,6,10,10-hexamethyl-4,7-dithiaundecanethiolato ligand formed by the ring-opening oligomerization of three 3,3-DMT molecules. Complex 3 was characterized crystallographically and was found to contain a bridging thiolato group and sigma-bonded carbon at the termini of the oligomer and one thioether group coordinated to an open cluster. Compound 1 does not oligomerize 3,3-DMT at 25-degrees-C. When heated to 125-degrees-C, 3 eliminated carbon monoxide and was transformed to two isomers Os3(CO)9[mu-SCH2CMe2CH2)3] 4 and 5 that contain closed triosmium clusters. Both also contain the same oligomeric grouping of the three 3,3-DMT ligands as in 3, but differ in the coordination position of the thiolato bridge. When heated to 120-degrees-C under 650 psi CO, compounds 3 and 5 were converted to Os3(CO)10[mu-O = C(CH2CMe2CH2S)3] (6), 68% by carbonylation. The C-terminus of the oligomer is functionalized by a CO group that bridges an open edge of the cluster in a mu-eta-2-O = C bridging mode. Both thioether groups are uncoordinated in 6. Compound 6 is decarbonylated at 68-degrees-C under nitrogen to yield Os3(CO)9[mu-O = C(CH2CMe2CH2S)3] (7), 46%. Compound 7 is similar to 6 except that one of the thioether groups of the oligomer is coordinated. Crystallographic data. For 2: space group P2(1)/c, a = 14.075 (3) angstrom, b = 22.143 (4) angstrom, c = 14.788 (3) angstrom, beta = 108.37 (2)o, Z = 2, 3227 reflections, R = 0.046. For 3: space group P1BAR, a = 12.025 (3) angstrom, b = 16.596 (4) angstrom, c = 9.738 (2) angstrom, alpha = 95.84 (2)o, beta = 108 76 (2)o, gamma = 79.96 (2)o, Z = 2, 2867 reflections, R = 0.029. For 4: space group P1BAR, a = 11.102 (2) angstrom, b = 14.724 (3) angstrom, c = 10.767 (2) angstrom, alpha = 104.94 (2)o, beta = 99.19 (1)o, gamma = 72.73 (1)o, Z = 2, 3519 reflections, R = 0.023. For 5: space group P2(1)/n, a = 15.153 (3) angstrom, b = 24.453 (7) angstrom, c = 10.359 (2) angstrom, beta = 90.58 (2)o, Z = 4, 2801 reflections, R = 0.031. For 6: space group P1BAR, a = 9.909 (2) angstrom, b = 20.642 (4) angstrom, c = 9.283 (2) angstrom, alpha = 101.30 (2)o, beta = 103.30 (2)o, gamma = 96.92 (2)o, Z = 2, 2568 reflections, R = 0.048. For 7: space group P2(1)/c, a = 12.256 (3) angstrom, b = 12.054 (2) angstrom, c = 23.110 (3) angstrom, beta = 103.53 (1)o, Z = 4, 3049 reflections, R = 0.033.